August 24, 2013

"tee" bash command for live streaming applications

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Dear all,
first time I post here, trying to find the best place to search help on my matter.

My basic problem is that: I want to make a "tee" command which would keep on working as a charm if one or multiple of the output pipes breaks or encounters any issue.

The background is the following:
I use a bunch of homemade bash script for some video recording/live streaming...

On key part of the video/audio path is that it is first grabbed from a firewire capture card, then go to a "tee" and from there is split to multiple application:
- Full quality dv recording
- live encoding and streaming to internet
- feed monitoring

As I can start and stop these "services" independently, I need to make sure that whatever happens, the "tee" keeps to taking the video from the capturing process and feed them to the services still alive without delaying (would cause frame drop) or anything similar.

Currently I use a modified version from the coreutils 5.0 (file attached, as well as diff from coreutils).

It works pretty well but I still see some cases where if my internet line drops (making the live stream encoding to pause or to break, the recording is also impacted.

However my C knowledge are not sufficient to see what more to do in this tee.c to reallly make it robust.
I expect something to do with signal handling but...

Could anyone give a hint, or point me to a better place if appropriate ?

Many thanks
Timothé

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